The present invention relates generally to a magnetic tape cassette, especially to a tape cassette for a video tape recorder. More specifically, the invention relates to a reel-lock mechanism for locking the tape reels in tape cassettes of any size.
As is well known, tape cassettes, especially tape cassettes for video tape recorders, which will be hereafter referred to as "VTR tape cassette", can accommodate various lengths of magentic tape, such as VTR tapes, within cassette casings of a single size designed to accommodated the longest desired length of magnetic tape. This necessarily leaves unnecessary empty space when a relatively short tape is housed in the cassette cover.
In the recent years, portable VTR systems have strived to be as compact as possible. This consideration naturally applies also to VTR tape cassettes. To satisfy this requirement, one approach has been to provide cassette casings of various sizes accommodating specific lengths of tape wound onto tape reels of a corresponding diameter. For instance, for a short tape, such as for a 10-minute recording, a small-diameter tape reel is used. In this case, a small cassette casing which will be referred to hereafter as "S size cassette cover" is used for housing the small-diameter tape reel. For a longer tape, such as for a 90-minute recording, a large-diameter tape reel and a large cassette casing, which is referred to as "L-size cassette casing", are used. Similarly, for a medium-length tape, such as for a 60-minute recording, a medium-diameter tape reel and medium-size cassette casing, which will be referred to as "M size cassette casing", are used.
Tape drive systems intended for use with various sizes of the tape reels and cassette casings must be adapted to deal with a broad range of cassette casing and tape handling requirements. For example, VTR systems capable of handling various sizes of VTR tape cassettes employ adjustable reel bases capable of driving tape reels of various sizes.
Such tape cassette product lines also require reel lock mechanisms for preventing the tape reels from rotating while the tape cassettes are not in use. Japanese Utility Model Publication (Jikko) Showa No. 58-7510, published on Feb. 9, 1983, discloses a tape reel lock mechanism in which the tape reels are released to be free to rotate by a vertical pin within the play-back unit, such as, a VTR player. A similar pin-actuated reel lock release has also been disclosed in Japanese Utility Model First Publication (Jikkai) Showa No. 58-114578, published on Aug. 5, 1983. When such conventional reel lock release mechanisms are adapted for use with tape cassettes of various sizes, a plurality of lock-release pins are required on the play-back unit. For instance, when S-, M-, L-size cassettes are all to be used, three lock-release pins are required due to different positions of the reel lock mechanisms of the different cassettes. In this case, the L-size cassette must have two extra holes simply to accommodate the pins for reel lock release for S- and M-size cassettes. To allow for the hole accommodating the pin for reel lock release for S-size cassettes, the tape reels of an L-size cassette must be inconveniently separated.